EP3974145A1 - Method and device for in situ marking a workpiece in a thermal forming process - Google Patents
Method and device for in situ marking a workpiece in a thermal forming process Download PDFInfo
- Publication number
- EP3974145A1 EP3974145A1 EP20198550.4A EP20198550A EP3974145A1 EP 3974145 A1 EP3974145 A1 EP 3974145A1 EP 20198550 A EP20198550 A EP 20198550A EP 3974145 A1 EP3974145 A1 EP 3974145A1
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- Prior art keywords
- workpiece
- heating elements
- heating
- predetermined
- marking
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Images
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
- B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
- B29C35/0266—Local curing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
- B29C71/02—Thermal after-treatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/02—Moulds or cores; Details thereof or accessories therefor with incorporated heating or cooling means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/42—Moulds or cores; Details thereof or accessories therefor characterised by the shape of the moulding surface, e.g. ribs or grooves
- B29C33/424—Moulding surfaces provided with means for marking or patterning
- B29C33/428—For altering indicia, e.g. data, numbers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C37/00—Component parts, details, accessories or auxiliary operations, not covered by group B29C33/00 or B29C35/00
- B29C37/0053—Moulding articles characterised by the shape of the surface, e.g. ribs, high polish
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/3415—Heating or cooling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
- B41M5/00—Duplicating or marking methods; Sheet materials for use therein
- B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B44—DECORATIVE ARTS
- B44B—MACHINES, APPARATUS OR TOOLS FOR ARTISTIC WORK, e.g. FOR SCULPTURING, GUILLOCHING, CARVING, BRANDING, INLAYING
- B44B7/00—Machines, apparatus or hand tools for branding, e.g. using radiant energy such as laser beams
- B44B7/007—Machines, apparatus or hand tools for branding, e.g. using radiant energy such as laser beams using a computer control means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B44—DECORATIVE ARTS
- B44C—PRODUCING DECORATIVE EFFECTS; MOSAICS; TARSIA WORK; PAPERHANGING
- B44C1/00—Processes, not specifically provided for elsewhere, for producing decorative surface effects
- B44C1/005—Processes, not specifically provided for elsewhere, for producing decorative surface effects by altering locally the surface material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
- B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
- B29C2035/0211—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould resistance heating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C37/00—Component parts, details, accessories or auxiliary operations, not covered by group B29C33/00 or B29C35/00
- B29C2037/80—Identifying, e.g. coding, dating, marking, numbering
Definitions
- the present invention relates to a method and device for in situ marking a workpiece in a thermal forming process, and a device for in-situ marking of a workpiecein a thermal forming process.
- EP 3 159 131 A1 discloses a device for marking a workpiece formed at least partially in a thermal master or forming process, wherein the device comprises a plurality of surface-distributed, individually controllable heating elements for a local heating of a workpiece surface, wherein each of the heating elements has a heating structure embedded in solid material, wherein the solid material has a surface structure directed to the workpiece surface, wherein the surface structure associated to a heating element has a predetermined or statistical topography and is heated at least partially by the heating structure.
- EP 3 159 131 A1 discloses the features of the preamble of present claim 1 and is related to a marking of formed pieces within the injection molding process, i.e. at the end of the process before ejecting the pieces so that each piece can be marked individually.
- US 3,961,575 relates to a printing apparatus having a back plate integrally connected to a ram capable of reciprocating or being stationary.
- the back plate has a surface that corresponds to the printing surface.
- a die carrying indicia is made to adjust to the contour of the printing surface automatically by use of spring bias means or resilient padding. Insert heaters are connected to each die.
- the device can be a tool or a tool insert for use as in-situ marking within the thermal forming process.
- the heating structure is preferably arranged in the solid material in a predetermined distance from the surface structure, especially behind a coating of the inner surface.
- the solid material of the heating elements can comprise a plurality of superimposed thin or thick layer produced or PCB printed layers. This allows a close arrangement of the heating elements behind the surface to be heated and a quicker direct impact of the heating energy on the darkening or foaming effect within the formed product/workpiece.
- the surface structure can be made of a low-wear material or coated with such low-wear material.
- the smooth surface of the entire marking area together with a low-wear material enhances the quality of the marking and the tool life.
- the heating elements can be arranged regularly, preferably in matrix form, allowing a free predetermined definition of the marking in the marking area. On the other side or additionally, heating elements can be arranged arbitrarily instead of a matrix form, then preferably as parts of letters, numbers, or decorative elements, e.g. as a 7-segment display.
- the heating elements can be electrical, (thermo)fluidic, optical or chemical heating elements.
- a system for marking a workpiece formed at least partially in a thermal forming or forming process comprises a device as mentioned above and a controller, wherein the controller is configured to energize the heating elements for heating one or more of them serially, in parallel or in groups to darken, burn or foam the surface of a workpiece formed in such a forming process and mold.
- a method for marking a workpiece in a thermal forming or forming process using the above mentioned system has a controller energizing predetermined heating elements for creating a predetermined marking through darkening, burning or foaming of the surface portion of the workpiece associated to said predetermined heating elements. This energizing action can occur while the forming process takes places, but certainly after the filling of the mold cavity with the workpiece material. Then, according to this embodiment, the workpiece material is in contact with the surface of the heating element.
- the invention is based on the insight that the surface structure directed to the workpiece surface is preferably smooth and even, since this embodiment of the method according to the invention is based on carbonization and foaming of the surface of the workpiece. This extends the life time of the heating surface and provides a surface of the work piece which bears a more easily readable marking. It it further noted that the rough surface (for smoothing) in contrast to the nanostructure is also less sensitive to wear, since a certain wear and tear has only a minor influence.
- the heating elements were heated to allow the plastics material to become liquid again and take the form of the surface of the work piece at the heated structure.
- the energy delivered to the individual heating elements of the array is high enough to alter the plastics material creating blisters or bubbles and changes its color to grey or black.
- altering comprises decomposing, disintegrating and deteriorating in the sense of: decomposing to foam, darken, crack or crosslink chemical bonds of the workpiece material to change color of the polymer or of an additive.
- the current delivered to the heating elements of the array chosen to be active is high enough to effect these thermic decomposition process which is known in the laser marking technology.
- the possible optical contrast is very high in view of the darkening blister creation.
- a further advantage of the present solution is the reduced costs for building such a form since no nanostructured surface is necessary but a simple smooth surface is ok which reduces beside the costs the necessity for the additional manufacturing step of the mold. Furthermore, the tool life is extended especially if workpieces made out of filled plastics are to be prepared which usually drastically reduced the life time of the nanostructure marking surfaces.
- the necessary optical contrast of the code provided by the marking distribution based on the heating elements is achieved through use of a smooth mold surface.
- the contrast is especially good for transparent or dark colored plastics (as it was by application of the prior art technique). Filled or reinforced plastics as well as brightly colored plastics can be marked with high contrast when using the teaching of the invention, i.e. when the heating creates foaming or disintegration.
- the workpiece surface is covered by a hard coating as prepared by Nitride or a Carbide layer or other known hard coatings.
- a hard coating as prepared by Nitride or a Carbide layer or other known hard coatings.
- Such a surface provides even after losing through wear minus several 100 nanometer layer coating the same functionality as the originally prepared work surface coating.
- the heating structure is arranged spaced from the surface structure in the solid material of the heating element advantageously between 10 nanometers and 100 micrometers.
- Heating structures are preferably ohmic conductors which, when energized, emit Joule heat as heat energy for heating, the heat reaching the surface structure mainly by means of heat conduction. This is in contrast to structures that try to heat the workpiece mainly with thermal radiation.
- a predetermined heating time is required to heat the workpiece surface to the extent that addressed surface portion can deteriorate and foam, i.e. have an effect far beyond a simple fusing of the work piece surface.
- the heating time is about 0.001 to 1 seconds.
- This heating can also comprise to provide sink marks, when the surface topography was already smooth.
- sink marks can be influenced upon, it is mainly a binary marking in front of each heating element: The sink-mark is created or it is not created.
- the surface different gray colours can be achieved, wherein the difference is mainly based upon the heat insertion which can be modulated over time or different heating energy. These markings are therefore not binary but can be distinguished between different shades of gray.
- the additive reacts at a certain threshold temperature, which is well above the processing temperature of the polymer but can be reached by the heating elements.
- the additive then might: change its color due to decomposition or forming of a new chemical bond (possible bonds: intra additive, inter additive or polymer-additive), change its fluorescence properties, liberate gas (N2, CO2,%) and present foaming, recrystallize, exsolve from the polymer, color change, carbonization etc. All of these will change the visual properties of the heated surface.
- Possible additives are inter alia hydrated zinc borate or compounds as disclosed in EP 0 675 001 A1 on page 3, lines 20 to 40. Flame retardants can also be used.
- the term "closed” for the mold status relates to a one-step marking during the thermal forming process.
- the term “opened” refers to an either one- or two-step marking process during and at the end of the thermal forming process; "one-step”, if the heating elements are only activated when the mold is opened; “two-step”, if the heating elements are (at least partially) activated when the mold is closed.
- Additive “yes” relates to the presence of an additive, wherby "(yes)" in brackets relates to an optional presence of such a heating sensitive additive.
- the marking occurs only in the "opened” state of the in-situ thermal forming, i.e. after the thermal forming step for the two embodiments smoothing or sink mark, wherein “smoothing” provides a glossy surface based on a original rough formed surface, wheras "sink mark” relates to the phenomenon of the same name in a otherwise smooth surface.
- the tool surface has a surface structure of the solid material in front of the heating elements.
- Said surface structure is an uniform surface over the entire front of the heating elements. It can be preferredly a smooth surface with a Ra-value of less than 100 nanometer or - especially for the smoothing embodiment an uniformly rough surface with a Ra-value of more than 1 micrometer. However, it is important for preferred embodiments that the Ra-value is not between 100 nanometer and 1 micrometer, which is the common technical feature of the preferred embodiments. Only the "sink mark" embodiment can use any surface with a clear preference for polished surfaces followed by rough surfaces but can also be applied for intermediate surfaces.
- each heating element front surface 2 has an extension in the micrometer to millimeter range, preferably with side lengths between from 10 micrometers to 5 millimeters.
- Each heating element front surface 2 is separated one from another by a web portion 9, preferably with a width of the order of 1 micron to 500 microns.
- Fig. 2 shows a view on the surface of the workpiece 6 having been formed with the tool / insert of Fig. 1 with symbolically shown heated areas 7.
- FIG. 2 it is possible to generate coding patterns in the underlying workpiece 6, which are comparable to a data matrix code or QR code. Such patterns can ideally be read by commercially available Data Matrix Code or QR Code readers.
- the heated areas 7 are shown in dark. However, the color of the heated area of the workpiece 6 does not darken necessarily. Within a foaming embodiment the heated areas become brighter.
- the tool or tool insert 1 includes a structure embedded therein or applied thereto, which has been produced by thin-film technology, thick-film technology, ceramic cofiring as HTCC or LTCC or PCB technology and which contains individually controllable inner heating structures 3.
- the surface of the heating element front surfaces 2 and of the additional in-between web portion structures 9 are smooth or polished with a Ra value of less than 100 nanometer. In a different embodiment the heating element front surfaces 2 the additional in-between web portion structures 9 are rough with a Ra-value of higher than 1 micrometer.
- the heater elements are in a preferred embodiment as close to the surface 7 and 70 as possible for a direct immediate heating effect. These two different tool inserts are available for the three different marking procedures, i.e. sink-mark generation, foaming and burning. Within an embodiment of marking in the opened state, the heating step can take place only in the open state, since the roughness of the front surface 2 can be so coarse that it is usually molded.
- the heating structure 3 can form at least part of the surface structure 40.
- the design of the heating structure 3, as well as the heat conduction in the solid material 11 of the mold or the heat conduction to the surface structure 40 determines which region can be shaped on a workpiece 6 and which region will not be altered.
- the surface 10 of the tool or tool insert 1 has a uniform surface finish, which can be produced by a surface treatment. Therefore the surface elements 2 as "shown" in Fig. 1 are not visible to the human eye, unless the heating cycle starts and then the result can be seen in the workpiece 6 as shown in Fig. 2 .
- FIG. 4 shows a plan view of the tool insert according to the invention as in FIG. 3 , wherein the filling molded workpiece 6' has a brighter color from the start than the workpiece 6 in FIG 3 .
- the difference between the molded workpiece 6 of Fig. 3 and the workpiece 6' of Fig. 4 is the heating effect on the workpiece 6, 6'.
- the darkened or burned surface structure 7' in the brighter workpiece 6' has usually a higher contrast than the darkened surface structure 7 in the darker workpiece 6.
- a seamless arrangement of the heating elements can create coherent impressions on the workpiece.
- an arrangement can be made available, which allows a very large number of possible marking combinations.
- the control of the heating elements 2 can either be taken over directly by a controller of a control unit of the original or forming machine or executed by a controller of a separate control device.
- the heating of the individual heating elements 2 takes place here either serially, in parallel or in groups one behind the other.
- a vertical cross section through the bottom three heating elements 2 of the second column from the left of the matrix arrangement in Fig. 1 is equal to the cross section shown in Fig 3
- the heating elements 2 shown here have square surface structures 4. Alternatively, these may be configured circular, elliptical or triangular, rectangular or the like.
- the heating elements 2 can be arranged in any area 100 in the solid material 11 of the tool / insert 1.
- the shape of the structure to be produced on the workpiece 6 can be predetermined by the choice of the shape of the heating structures 3.
- Fig. 5 shows a schematic side sectional view through a tool / insert 1 according to an embodiment of the invention with a just formed and smoothened workpiece region 7". Therefore, the workpiece 6" and tool insert 1 are shown in a distance one from another.
- the tool insert 1 comprises a roughened tool surface 10", preferably also covering the separating web portion 9.
- these roughened surface structures of the tool surface 10" are formed when the mold is closed. Upon opening the mold, there is a subsequent heating step.
- Fig. 6 shows a schematic side sectional view through a tool / insert 1 according to an embodiment of the invention with a just formed and differently altered workpiece region 7"'.
- the workpiece 6'" and tool insert 1 are shown in a distance one from another like in Fig. 5 .
- the tool surface 10 is smooth as in the embodiments shown in Fig. 3 and 4 .
- the difference is the creation of sink marks 17 in the framework of sink mark surface portion 7'" with elevated edges.
- not heating the heating structure 3 leaves the surface portion 70 unaltered and smooth as a smooth unaltered surface portion 70, whereas the subsequent heating via the heat input 5 during the opening step or during an intermediate interval after moving the mold a predetermined distance apart provides....
- the heat sink 17 with edges as altered surface portion 7"'.
- Fig. 7A to Fig. 7F shows schematic side sectional views through a detail of the tool / insert of Fig. 6 from start of the method until the completion of a sink mark generation using not fully closed mold.
- the detail view shows one single heating structure 3 without the solid material of the tool insert 1 facing the unaltered surface portion 70 of workpiece 6"'. The mold is no longer completely closed, the heating structure 3 is already retracted providing the gap between the smooth surface in front of the heating structure 3 and the facing unaltered surface portion 70.
- unaltered surface portion 70 of the workpiece 6 is essentially flat and in front of the flat tool surface 10 (not shown in Fig. 7A to 7F ). Then a voltage V is applied between the free ends of the heating structure 3, as shown in Fig. 7B . Therefore, a heat input 5 is provided and melts the surface area of a liquefied surface portion 71 of the workpiece 6'" facing the heating structure 3.
- the liquefied surface portion 71 has a width covering essentially the area covered by the heating structure 3 and melts the surface area 70 of the workpiece 6'" with a rounded convex form.
- the liquefied surface portion 71 extends above the level of the cold unaltered surface portion 70 and creates a circular ridge 72.
- the ridge 72 has circular and there similar dimensions in view of the definition that the heating element front surface 2 of the preferred embodiments is of a square dimension.
- Fig. 7C shows the step after the heating step. Therefore, the heating structure 3 is no longer connected to the voltage supply.
- the liquefied polymer is flowing and creates a slight inner depression 73 showing the circular ridge 72.
- the inner core 74 of the liquefied surface portion 71 remains liquid, whereas the surface portions itself 75 begins to solidify as shown with the line encompassing the liquid inner core 74.
- the edge zone of the molten polymer portion becomes solid again, reducing the total volume and causing the upper surface layer 77 to sink in slightly.
- the layer thickness of the solidified edge zone and of the upper surface layer 77 increases continuously, whereby the total volume decreases continuously and the loss of volume is compensated by further sinking of the top surface layer 77 in the center of the heated area. Therefore, the reference numeral 77 for this slightly hardening top surface layer is only used in Fig. 7C to 7E , since in Fig. 7B there is no such top layer 77 and in Fig. 7E the hardening is already completed
- Fig. 7D and Fig. 7E show further steps of solidifying of the liquefied polymer 71 with a thicker solidified surface portion 75 and a shrinking still liquefied core, accentuating the inner depression 73, thus raising the circular ridge 72.
- Fig. 7F finally shows the final solidified status of the former liquefied surface portion.
- the now complete solid surface portion 75 is not separated from the unaltered surface portion.
- the still shown boundary line is explanatory.
- the main feature of workpiece 6"' is the flat unaltered surface portion changing to an elevated ridge 72 to an inner depression 73 creating the sink mark 17 as shown in Fig. 6 .
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Optics & Photonics (AREA)
- Health & Medical Sciences (AREA)
- Oral & Maxillofacial Surgery (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
- Shaping Of Tube Ends By Bending Or Straightening (AREA)
Abstract
Description
- The present invention relates to a method and device for in situ marking a workpiece in a thermal forming process, and a device for in-situ marking of a workpiecein a thermal forming process.
- From
DE 102 42 565A1 a method has become known in which the marking takes place by generating convex curvatures in the material surface by supplying electromagnetic radiation through a cavity. -
EP 3 159 131 A1 -
EP 3 159 131 A1present claim 1 and is related to a marking of formed pieces within the injection molding process, i.e. at the end of the process before ejecting the pieces so that each piece can be marked individually. -
US 3,961,575 relates to a printing apparatus having a back plate integrally connected to a ram capable of reciprocating or being stationary. The back plate has a surface that corresponds to the printing surface. A die carrying indicia is made to adjust to the contour of the printing surface automatically by use of spring bias means or resilient padding. Insert heaters are connected to each die. - Providing nanostructures in the surface created by an array of heating elements does not allow using the method and such a device for all kinds of plastics and colors. The prior art method is more efficient on dark plastics and cannot be used for brightly colored plastics.
- It is therefore an object of the present invention to provide a device and method for in-situ marking a workpiece which is formed at least partially in a thermal master or forming process which allows readability of such codes with simpler reading devices at a larger range of plastics and colors of the formed pieces.
- A further issue with the method of the prior art is the wear of the nanostructures at the surface structure directed to the workpiece surface. The nanostructures surface becomes less performant after a limited number of formed pieces. It is therefore a further object of the present invention to provide a device and method marking in-situ of a workpiece formed at least partially in a thermal master or forming process which allows a longer tool life.
- The device used in a method according to the invention for marking a workpiece, when said workpiece is formed at least partially in a thermal master or forming process, comprises a surface directed towards the workpiece, wherein a number of individually controllable heating elements is distributed behind the surface for a local heating of a workpiece surface portion. Then each of the heating elements comprises a solid material having a surface structure and a heating structure, wherein the surface directed towards the workpiece encompassing the surface structures has either a roughened surface having a Ra-value of greater 1 micrometer or a uniform smooth surface having a Ra-value of less than 100 nanometer allowing to darken, burn or foam the surface of the workpiece through heat introduction.
- The device can be a tool or a tool insert for use as in-situ marking within the thermal forming process.
- The heating structure is preferably arranged in the solid material in a predetermined distance from the surface structure, especially behind a coating of the inner surface. The solid material of the heating elements can comprise a plurality of superimposed thin or thick layer produced or PCB printed layers. This allows a close arrangement of the heating elements behind the surface to be heated and a quicker direct impact of the heating energy on the darkening or foaming effect within the formed product/workpiece.
- The surface structure can be made of a low-wear material or coated with such low-wear material. The smooth surface of the entire marking area together with a low-wear material enhances the quality of the marking and the tool life.
- The heating elements can be arranged regularly, preferably in matrix form, allowing a free predetermined definition of the marking in the marking area. On the other side or additionally, heating elements can be arranged arbitrarily instead of a matrix form, then preferably as parts of letters, numbers, or decorative elements, e.g. as a 7-segment display.
- The heating elements can be electrical, (thermo)fluidic, optical or chemical heating elements.
- A system for marking a workpiece formed at least partially in a thermal forming or forming process comprises a device as mentioned above and a controller, wherein the controller is configured to energize the heating elements for heating one or more of them serially, in parallel or in groups to darken, burn or foam the surface of a workpiece formed in such a forming process and mold.
- A method for marking a workpiece in a thermal forming or forming process, using the above mentioned system has a controller energizing predetermined heating elements for creating a predetermined marking through darkening, burning or foaming of the surface portion of the workpiece associated to said predetermined heating elements. This energizing action can occur while the forming process takes places, but certainly after the filling of the mold cavity with the workpiece material. Then, according to this embodiment, the workpiece material is in contact with the surface of the heating element.
- It is also possible to modify the in-situ method of marking the workpiece to heat the heating elements only while the mold is already opening. Then the workpiece is no longer in direct contact with the heating surface of the device but in close relationship with a distance between the surface of the workpiece and the surface of the associated heating element of between 0.001 and 1 millimeters. The distance is predetermined that the darkening or foaming effect still takes places. Here, the change of the surface occurs based on local heating of the workpiece through thermal radiation. The advantage of the two-step approach is based on the darkening and smoothening action of the thermal radiation in a small distance of the workpiece, small enough to heat the surface but large enough to allow a smoothening material flow. It is possible to form a rough surface based on a rough inner surface of the insert with a tool surface with a Ra-value greater than 1 micrometer. Then heating of the workpiece, even in presence of a rough inner surface of the insert, locally smoothens the workpiece and increases the contrast between smoothened and original workpiece portions.
- The invention is based on the insight that the surface structure directed to the workpiece surface is preferably smooth and even, since this embodiment of the method according to the invention is based on carbonization and foaming of the surface of the workpiece. This extends the life time of the heating surface and provides a surface of the work piece which bears a more easily readable marking. It it further noted that the rough surface (for smoothing) in contrast to the nanostructure is also less sensitive to wear, since a certain wear and tear has only a minor influence.
- Within the prior art method according to
EP 3 159 131 A1 - It is an advantage of the present invention to provide a method which can be applied to plastics of light color, filled or crystalline plastics as well as reinforced plastics, i.e. plastics where the method according to the prior art provide a non-satisfactory effect.
- A further advantage of the present solution is the reduced costs for building such a form since no nanostructured surface is necessary but a simple smooth surface is ok which reduces beside the costs the necessity for the additional manufacturing step of the mold. Furthermore, the tool life is extended especially if workpieces made out of filled plastics are to be prepared which usually drastically reduced the life time of the nanostructure marking surfaces.
- The necessary optical contrast of the code provided by the marking distribution based on the heating elements is achieved through use of a smooth mold surface. The contrast is especially good for transparent or dark colored plastics (as it was by application of the prior art technique). Filled or reinforced plastics as well as brightly colored plastics can be marked with high contrast when using the teaching of the invention, i.e. when the heating creates foaming or disintegration.
- Preferably, the workpiece surface is covered by a hard coating as prepared by Nitride or a Carbide layer or other known hard coatings. Such a surface provides even after losing through wear minus several 100 nanometer layer coating the same functionality as the originally prepared work surface coating.
- Preferably, the device is a tool or a tool insert for a thermal forming process, preferably for thermoformable plastics.
- In a preferred embodiment, the heating structure is arranged spaced from the surface structure in the solid material of the heating element advantageously between 10 nanometers and 100 micrometers.
- Heating structures are preferably ohmic conductors which, when energized, emit Joule heat as heat energy for heating, the heat reaching the surface structure mainly by means of heat conduction. This is in contrast to structures that try to heat the workpiece mainly with thermal radiation.
- Depending on the nature of the workpiece material, a predetermined heating time is required to heat the workpiece surface to the extent that addressed surface portion can deteriorate and foam, i.e. have an effect far beyond a simple fusing of the work piece surface. Preferably, the heating time is about 0.001 to 1 seconds.
- Smoothing of initially roughened surfaces, which is understood in the framework of this description to have a tool Ra-value of greater than 1 micrometer, creates a greater contrast between the then smoothened surfaces so that this is achieved with a two step process. The first step comprises the thermal forming process with an initial rough surface of workpiece surface with closed mold, wherein the rough surface is due to the tool surface in front of the heating elements, but which heating elements are not heated in this first step. This first step is followed by a second step with partly opened mold with the tool/insert surface in a predetermined distance to apply a heating round smoothening the initially rough surface.
- This heating can also comprise to provide sink marks, when the surface topography was already smooth. Although the structure of sink marks can be influenced upon, it is mainly a binary marking in front of each heating element: The sink-mark is created or it is not created.
- Within the burning (=darkening) or foaming (=brightening) the surface different gray colours can be achieved, wherein the difference is mainly based upon the heat insertion which can be modulated over time or different heating energy. These markings are therefore not binary but can be distinguished between different shades of gray.
- It is possible to open the mold, e.g. between 0,001 to 1 millimetres, to apply the heating step. It is also possible to have the mold closed but with a relieved locking unit to apply the a heating step, either a single heating step or a second heating step, when a first heating step was provided in the fully closed state.
- It is possible to obtain the effect of improved contrast by creating sinkmarks. Based on an volume enhancement of the polymer when liquefied by the heater, it forms a local hump. This happens only when the mold is not closed anymore. When the heater is turned off, the polymer solidifies again beginning at the surface portion while the volume is still enhanced. The solidification proceeds while the polymer shrinks again, which forms a sink mark. The volume of the molten material is the same before and after the marking process, but it's distribution is changed from the unaltered surface.
- A further possibility is the use of an additive as part of the composition of the injection molding polymer. Such particles or molecules are added to the original polymer before processing (e.g. as so called "master batch"). This is common practice in laser marking, where the carbonization or foaming of the injection molded part is (in some cases) only possible with an additive. In the case of the laser the additive acts as an optical absorbing material which converts the optical energy of the laser into thermal energy, when the polymer itself absorbs only little. In the present case, the amount of available energy is not so relevant and can be lower compared to a laser, since the heat energy transfer to the polymer is not the critical aspect. The additive is the molecule or particle that is directly altered. The additive reacts at a certain threshold temperature, which is well above the processing temperature of the polymer but can be reached by the heating elements. The additive then might: change its color due to decomposition or forming of a new chemical bond (possible bonds: intra additive, inter additive or polymer-additive), change its fluorescence properties, liberate gas (N2, CO2,...) and present foaming, recrystallize, exsolve from the polymer, color change, carbonization etc.. All of these will change the visual properties of the heated surface. Possible additives are inter alia hydrated zinc borate or compounds as disclosed in
EP 0 675 001 A1 onpage 3, lines 20 to 40. Flame retardants can also be used. - The wording that the method happens in a thermal forming process comprises the fact and embodiments, where the marking method step is conducted after (slight) opening of the mold, i.e. at the end of the forming process, when the workpiece is already formed, but not (completely) marked. It is considered that the thermal forming process comprises the marking and is only considered completed after the marking took place and the work piece is ejected from the thermal forming machine.
- The table shows different embodiments according to the invention:
Embodiment Tool surface Mold status Additive Appearance change Foaming Polished Opened/Closed Yes brighter (especially for darker polymers) Burning Polished Opened/Closed No / (yes) darker (especially for brighter polymers) Smoothing Rough Opened No / (yes) gloss instead of rough Sink mark (Rough)/Polished Opened No / (yes) visible sink mark - The term "closed" for the mold status relates to a one-step marking during the thermal forming process. The term "opened" refers to an either one- or two-step marking process during and at the end of the thermal forming process; "one-step", if the heating elements are only activated when the mold is opened; "two-step", if the heating elements are (at least partially) activated when the mold is closed. Additive "yes" relates to the presence of an additive, wherby "(yes)" in brackets relates to an optional presence of such a heating sensitive additive.
- The marking occurs only in the "opened" state of the in-situ thermal forming, i.e. after the thermal forming step for the two embodiments smoothing or sink mark, wherein "smoothing" provides a glossy surface based on a original rough formed surface, wheras "sink mark" relates to the phenomenon of the same name in a otherwise smooth surface.
- "Foaming" and "Burning" can be conducted in a closed environment, but the development of the foamed surface and the burning under external oxygen from the air improves the effect over an embodiment with a closed mold.
- The tool surface has a surface structure of the solid material in front of the heating elements. Said surface structure is an uniform surface over the entire front of the heating elements. It can be preferredly a smooth surface with a Ra-value of less than 100 nanometer or - especially for the smoothing embodiment an uniformly rough surface with a Ra-value of more than 1 micrometer. However, it is important for preferred embodiments that the Ra-value is not between 100 nanometer and 1 micrometer, which is the common technical feature of the preferred embodiments. Only the "sink mark" embodiment can use any surface with a clear preference for polished surfaces followed by rough surfaces but can also be applied for intermediate surfaces.
- Further embodiments of the invention are laid down in the dependent claims.
- Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,
- Fig. 1
- shows a schematical plan view on the surface of a tool / insert according to an embodiment of the invention with usually not visible heating element surface areas;
- Fig. 2
- shows a schematical plan view on the surface of the workpiece having been formed with the tool / insert of
Fig. 1 with symbolically shown heated areas; - Fig. 3
- shows a schematic side sectional view through a tool / insert according to an embodiment of the invention with a just formed workpiece;
- Fig. 4
- shows a schematic side sectional view through a tool / insert according to an embodiment of the invention with a just formed workpiece region;
- Fig. 5
- shows a schematic side sectional view through a tool / insert according to an embodiment of the invention with a just formed and smoothened workpiece region;
- Fig. 6
- shows a schematic side sectional view through a tool / insert according to an embodiment of the invention with a just formed and differently altered workpiece region; and
- Fig. 7A to 7F
- shows schematic side sectional views through a detail of the tool / insert of
Fig. 6 from start until the completion of a sink mark generation using not fully closed mold. -
FIG. 1 shows a schematical plan view on the surface of a tool /insert 1 according to an embodiment of the invention with usually not visible heating elementfront surface areas 2 on thetool surface 10, i.e. thetool surface 10 appears to the human eye flat and no features can be distinguished. The different heating element front surfaces 2 are shown as areas which can be heated according to the signals of a control unit. - The heating elements, responsible for heating up the heating element front surfaces 2, and which heating elements are shown in
Fig. 3 and 4 , are distributed in matrix form, wherein each heating elementfront surface 2 has an extension in the micrometer to millimeter range, preferably with side lengths between from 10 micrometers to 5 millimeters. Each heating elementfront surface 2 is separated one from another by aweb portion 9, preferably with a width of the order of 1 micron to 500 microns. Of course, it is not necessary to have square heating element front surfaces 2 but information is usually shown in pixel and every heating elementfront surface 2 is intended to provide one pixel of information. - Alternatively, there may be an optically unobservable distance between the individual heating element
front surface areas 2, i.e. the individual heating elementfront surface areas 2 are adjacent one beside another.Fig. 1 shows an arrangement of eight by eight heating elements with squareheatable surface structures 40, which are spaced from one another through saidweb portions 9 of equal width. -
Fig. 2 shows a view on the surface of theworkpiece 6 having been formed with the tool / insert ofFig. 1 with symbolically shownheated areas 7. As shown inFIG. 2 , it is possible to generate coding patterns in theunderlying workpiece 6, which are comparable to a data matrix code or QR code. Such patterns can ideally be read by commercially available Data Matrix Code or QR Code readers. Theheated areas 7 are shown in dark. However, the color of the heated area of theworkpiece 6 does not darken necessarily. Within a foaming embodiment the heated areas become brighter. - The tool or
tool insert 1 includes a structure embedded therein or applied thereto, which has been produced by thin-film technology, thick-film technology, ceramic cofiring as HTCC or LTCC or PCB technology and which contains individually controllableinner heating structures 3. - The surface of the heating element front surfaces 2 and of the additional in-between
web portion structures 9 are smooth or polished with a Ra value of less than 100 nanometer. In a different embodiment the heating element front surfaces 2 the additional in-betweenweb portion structures 9 are rough with a Ra-value of higher than 1 micrometer. The heater elements are in a preferred embodiment as close to thesurface front surface 2 can be so coarse that it is usually molded. - The
tool insert 1 with the describedheating elements 3 can be assigned to any position of theworkpiece 6 within an arbitrary area. - In the embodiment shown in
FIG. 1 , theheating structure 3 can form at least part of thesurface structure 40. -
FIG. 3 shows a schematic lateral sectional view through a tool insert according to the embodiment ofFig. 1 according to the invention with asolid workpiece 6, as shown inFig. 2 , wherein theindividual heating elements 3, or theirsurface structures 40, are arranged next to each other with asmall spacing 9. - The design of the
heating structure 3, as well as the heat conduction in thesolid material 11 of the mold or the heat conduction to thesurface structure 40 determines which region can be shaped on aworkpiece 6 and which region will not be altered. - The
surface 10 of the tool ortool insert 1 has a uniform surface finish, which can be produced by a surface treatment. Therefore thesurface elements 2 as "shown" inFig. 1 are not visible to the human eye, unless the heating cycle starts and then the result can be seen in theworkpiece 6 as shown inFig. 2 . -
FIG. 4 shows a plan view of the tool insert according to the invention as inFIG. 3 , wherein the filling molded workpiece 6' has a brighter color from the start than theworkpiece 6 inFIG 3 . The difference between the moldedworkpiece 6 ofFig. 3 and the workpiece 6' ofFig. 4 is the heating effect on theworkpiece 6, 6'. The darkened or burned surface structure 7' in the brighter workpiece 6' has usually a higher contrast than thedarkened surface structure 7 in thedarker workpiece 6. - A further difference between the two
workpiece 6, 6'surface structures 7 and 7' can occur based on the material of theworkpiece 6 or 6'. Beside a darkening effect, it is also possible that theheating elements 2 heat thesurface 2 in a way with a sufficient heat introduction that the material is foaming and/or partially destroyed so that a surface degradation appears insuch surface areas 7 and 7'. Foaming is specifically suitable fordarker workpieces 6, because this generatesbrighter surface portions 7, which is not as advantageous for brighter workpieces 6', where darkening by carbonization 7' is preferred. - A seamless arrangement of the heating elements (without web-space 9) can create coherent impressions on the workpiece. By the number of juxtaposed and stacked heating elements, an arrangement can be made available, which allows a very large number of possible marking combinations.
- The control of the
heating elements 2 can either be taken over directly by a controller of a control unit of the original or forming machine or executed by a controller of a separate control device. - In the second case, the heating process, i.e. the heating of the
heating structure 3 of therespective heating element 2 is triggered by the original or forming process. - The heating of the
individual heating elements 2 takes place here either serially, in parallel or in groups one behind the other. - A vertical cross section through the bottom three
heating elements 2 of the second column from the left of the matrix arrangement inFig. 1 is equal to the cross section shown inFig 3 - Since only the upper and
lower heating elements 3 experience aheat input 5, only theirsurface structure 2 is transferred to theworkpiece 6 and produce there an opticallyrecognizable imprint 7, i.e. light scattering surfaces or burnedsurface portions 7, while the region of the central (second)heating element 2 in theworkpiece 6 produces no impression and leaves a substantiallyreflective surface 70 on theworkpiece 6. - The same distribution of
heated elements 2 could also be seen in the cross section shown inFig 4 for a horizontal cross section through the first threeheating elements 2 of the top row, since the arrangement is configured substantially the same in both directions. - The
heating elements 2 shown here have square surface structures 4. Alternatively, these may be configured circular, elliptical or triangular, rectangular or the like. Theheating elements 2 can be arranged in anyarea 100 in thesolid material 11 of the tool /insert 1. - In a uniform embodiment of all
surface structures 40, the shape of the structure to be produced on theworkpiece 6 can be predetermined by the choice of the shape of theheating structures 3. -
Fig. 5 shows a schematic side sectional view through a tool /insert 1 according to an embodiment of the invention with a just formed and smoothenedworkpiece region 7". Therefore, theworkpiece 6" andtool insert 1 are shown in a distance one from another. Thetool insert 1 comprises a roughenedtool surface 10", preferably also covering the separatingweb portion 9. Here, these roughened surface structures of thetool surface 10" are formed when the mold is closed. Upon opening the mold, there is a subsequent heating step. Therein, not heating theheating structure 3 leaves thesurface portion 70 unaltered and rough as a roughenedunaltered surface portion 70, whereas the subsequent heating via theheat input 5 during the opening step or during an intermediate interval after moving the mold a predetermined distance apart smoothens the heated surface portions to smoothenedsurface portions 7". This is a different alteration of the altered surface portions, here smoothenedsurface portions 7" before ejecting theworkpiece 6" after said subsequent heating interval. -
Fig. 6 shows a schematic side sectional view through a tool /insert 1 according to an embodiment of the invention with a just formed and differently alteredworkpiece region 7"'. The workpiece 6'" andtool insert 1 are shown in a distance one from another like inFig. 5 . Thetool surface 10 is smooth as in the embodiments shown inFig. 3 and 4 . The difference is the creation of sink marks 17 in the framework of sink mark surface portion 7'" with elevated edges. Therein, not heating theheating structure 3 leaves thesurface portion 70 unaltered and smooth as a smoothunaltered surface portion 70, whereas the subsequent heating via theheat input 5 during the opening step or during an intermediate interval after moving the mold a predetermined distance apart provides.... Theheat sink 17 with edges as alteredsurface portion 7"'. This is a different alteration of the altered surface portions, here surfaceportions 7"' before ejecting the workpiece 6'" after said subsequent heating interval. -
Fig. 7A to Fig. 7F shows schematic side sectional views through a detail of the tool / insert ofFig. 6 from start of the method until the completion of a sink mark generation using not fully closed mold. The detail view shows onesingle heating structure 3 without the solid material of thetool insert 1 facing theunaltered surface portion 70 ofworkpiece 6"'. The mold is no longer completely closed, theheating structure 3 is already retracted providing the gap between the smooth surface in front of theheating structure 3 and the facingunaltered surface portion 70. - Initially, as shown in
Fig. 7A ,unaltered surface portion 70 of theworkpiece 6 is essentially flat and in front of the flat tool surface 10 (not shown inFig. 7A to 7F ). Then a voltage V is applied between the free ends of theheating structure 3, as shown inFig. 7B . Therefore, aheat input 5 is provided and melts the surface area of a liquefiedsurface portion 71 of the workpiece 6'" facing theheating structure 3. The liquefiedsurface portion 71 has a width covering essentially the area covered by theheating structure 3 and melts thesurface area 70 of the workpiece 6'" with a rounded convex form. Since heated polymer material takes more place, the liquefiedsurface portion 71 extends above the level of the coldunaltered surface portion 70 and creates acircular ridge 72. Theridge 72 has circular and there similar dimensions in view of the definition that the heating elementfront surface 2 of the preferred embodiments is of a square dimension. -
Fig. 7C shows the step after the heating step. Therefore, theheating structure 3 is no longer connected to the voltage supply. The liquefied polymer is flowing and creates a slightinner depression 73 showing thecircular ridge 72. The inner core 74 of the liquefiedsurface portion 71 remains liquid, whereas the surface portions itself 75 begins to solidify as shown with the line encompassing the liquid inner core 74. The edge zone of the molten polymer portion becomes solid again, reducing the total volume and causing theupper surface layer 77 to sink in slightly. As the process continues, the layer thickness of the solidified edge zone and of theupper surface layer 77 increases continuously, whereby the total volume decreases continuously and the loss of volume is compensated by further sinking of thetop surface layer 77 in the center of the heated area. Therefore, thereference numeral 77 for this slightly hardening top surface layer is only used inFig. 7C to 7E , since inFig. 7B there is no suchtop layer 77 and inFig. 7E the hardening is already completed. -
Fig. 7D and Fig. 7E show further steps of solidifying of the liquefiedpolymer 71 with a thicker solidifiedsurface portion 75 and a shrinking still liquefied core, accentuating theinner depression 73, thus raising thecircular ridge 72.Fig. 7F finally shows the final solidified status of the former liquefied surface portion. Of course, the now completesolid surface portion 75 is not separated from the unaltered surface portion. The still shown boundary line is explanatory. The main feature ofworkpiece 6"' is the flat unaltered surface portion changing to anelevated ridge 72 to aninner depression 73 creating thesink mark 17 as shown inFig. 6 .LIST OF REFERENCE SIGNS 1 tool insert 10" tool surface 2 heating element front surface 11 solid material 3 heating structure 17 sink mark 5 heat input 40 square heatable surface structure 6 workpiece 6' workpiece 60 work piece surface 6" workpiece 70 unaltered surface portion 6"' workpiece 71 liquefied surface portion 7 "burned" surface portion 72 circular ridge 7' darker or lighter surface portion 73 inner depression 74 liquid inner core 7" smoothened surface portion 75 solidified surface portion 7"' sink mark surface portion 77 central top sinking-in layer 8 electric line 100 border of the tool insert 9 separating web portion 600 border of work piece relating to tool insert 10 tool surface
Claims (15)
- A method for in-situ marking a workpiece (6, 6') in a thermal forming process of a polymer material, using a device (1) comprising a surface (10) directed towards the workpiece (6, 6'), wherein a number of heating elements (2) is distributed behind the surface (10) for a local heating of a workpiece surface portion (60), wherein each of the heating elements (2) comprises a solid material (11) having a surface structure (40) and a heating structure (3), wherein the device further comprises a controller connected to the individually controllable heating elements (2), wherein the method comprises the step to energize predetermined heating elements (2, 3) through control signals from the controller for creating a predetermined marking through altering the surface portion of the workpiece comprising an altering taken from the group encompassing darkening, burning, foaming of the surface portion (7) of the workpiece (6, 6') associated to said predetermined heating elements (2, 3) or creation of altered, especially darker or lighter molecules in the surface portion (7) of the workpiece (6, 6') compared to adjacent surface portions of the workpiece (6, 6').
- The method of claim 1, wherein the method step of energizing the predetermined heating elements (2) by the control unit is applied only after the opening of the mold of the thermal forming process when the workpiece (6, 6') is no longer in direct contact with the heating surface (10) of the device (1) but in close relationship with a predetermined mean distance between the surface (7) of the workpiece (6, 6') and the surface (2) of the associated heating element (2, 3).
- The method of claim 2, wherein the control unit provides a predetermined energizing of the predetermined heating elements (2) to liquefy the surface of the workpiece, followed by a solidification step creating sink marks at the surface portions vis-à-vis the predetermined energized heating elements (2).
- The method of claim 2, wherein the control unit provides a predetermined energizing of the predetermined heating elements (2) to smooth the rough surface of the workpiece with a Ra-value of more than 1 micrometer, followed by a solidification step creating a glossy surface at the surface portions vis-à-vis the predetermined energized heating elements (2).
- The method of claim 1, wherein the control unit provides a double marking step; a first marking step when the mold is closed leading to a forming of a roughened surface at the corresponding heated places at the predetermined heating elements (2) and a second marking step when the mold is slightly opened with a predetermined mean distance between the surface (7) of the workpiece (6, 6') and the surface (2) of the associated heating element (2, 3) leading to a forming of a smoothed previously rougher surface at the corresponding heated places.
- The method according to any one of claims 1 to 5, wherein the surface structure (40) of the solid material is an uniform smooth surface with a Ra-value of less than 100 nanometer or an uniformly rough surface with a Ra-value of more than 1 micrometer.
- The method according to any one of claims 1 to 6, wherein an additive is mixed within the polymer material used in the thermal forming process, wherein the additive is chosen from chemical compounds taken from the group which changes its color due to decomposition or forming of a new intra-additive, inter-additive or polymer-additive chemical bond, change its fluorescence properties, liberate a gas or present foaming, recrystallization, exsolvation from the polymer, color change or carbonization, upon heating within the in-situ marking method.
- A device (1) for in situ marking of a workpiece (6, 6') with the method of any one of claims 1 to 7, wherein the workpiece (6, 6') is formed in a thermal master or forming process, wherein the device (1) is a tool or a tool insert for a thermal forming process, wherein the device (1) comprises a surface (10) directed towards the workpiece (6, 6'), wherein a number of individually controllable heating elements (2) is distributed behind the surface (10) for a local heating of a workpiece surface portion (60), wherein each of the heating elements (2) comprises a solid material (11) having a surface structure (40) and a heating structure (3), wherein the device further comprises a controller connected to the individually controllable heating elements (2) and configured to energize predetermined heating elements (2, 3) through control signals, wherein the surface (10) directed towards the workpiece (6, 6') encompassing the surface structures (40) has a uniform surface, especially an uniform smooth surface with a Ra-value of less than 100 nanometer or an uniformly rough surface with a Ra-value of more than 1 micrometer.
- The device (1) according to claim 8, wherein the surface structure (40) comprises at least a portion of the surface (10) to be directed against the workpiece (6).
- The device (1) according to one of claims 8 or 9, wherein the heating structure (3) in the solid material (11) is positioned in a predetermined distance from the surface structure (40).
- The device (1) according to any one of claims 8 to 10, wherein the solid material (11) of the heating elements (2, 3) comprises a plurality of superimposed thin or thick layer produced or PCB printed layers.
- The device (1) according to any one of claims 8 to 11 wherein the surface structure (40) is made of a low-wear material or coated with such low-wear material.
- The device (1) according to any one of claims 8 to 12, wherein the heating elements (2, 3) are arranged regularly, preferably in matrix form.
- The device (1) according to any one of claims 8 to 13, wherein the heating elements (2, 3) are arranged arbitrarily, preferably as parts of letters, numbers, or decorative elements.
- The device (1) according to any one of claims 8 to 14, wherein the control unit is configured allowing to heat the heating elements (3) when the mold of the device is partially open so that the front surface (70) of the device with heating elements (3) arranged behind the front surface (70) is in a predetermined distance from the workpiece surface.
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EP20198550.4A EP3974145B1 (en) | 2020-09-25 | 2020-09-25 | Method for in situ marking a workpiece in a thermal forming process |
US17/480,271 US11691362B2 (en) | 2020-09-25 | 2021-09-21 | Method and device for in situ marking a workpiece in a thermal forming process |
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EP20198550.4A EP3974145B1 (en) | 2020-09-25 | 2020-09-25 | Method for in situ marking a workpiece in a thermal forming process |
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EP0675001A1 (en) | 1994-03-29 | 1995-10-04 | Ge Plastics Japan Limited | Resin compositions for laser marking |
DE10242565A1 (en) | 2001-10-01 | 2003-04-10 | Cpar Ag Degersheim | Method and device for workpiece designation |
US20150017390A1 (en) * | 2013-07-12 | 2015-01-15 | Panasonic Corporation | Molding method for fiber reinforced composite material and molding apparatus for fiber reinforced composite material |
EP3159131A1 (en) | 2015-10-19 | 2017-04-26 | Interstaatliche Hichschule für Technik NTB Buchs | Device for marking workpieces |
US20190329465A1 (en) * | 2018-04-25 | 2019-10-31 | NTB Interstaatliche Hochschule für Technik Buchs | Mold and Device for Marking Work Pieces |
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2020
- 2020-09-25 EP EP20198550.4A patent/EP3974145B1/en active Active
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2021
- 2021-09-21 US US17/480,271 patent/US11691362B2/en active Active
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EP0675001A1 (en) | 1994-03-29 | 1995-10-04 | Ge Plastics Japan Limited | Resin compositions for laser marking |
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US20150017390A1 (en) * | 2013-07-12 | 2015-01-15 | Panasonic Corporation | Molding method for fiber reinforced composite material and molding apparatus for fiber reinforced composite material |
EP3159131A1 (en) | 2015-10-19 | 2017-04-26 | Interstaatliche Hichschule für Technik NTB Buchs | Device for marking workpieces |
US20190329465A1 (en) * | 2018-04-25 | 2019-10-31 | NTB Interstaatliche Hochschule für Technik Buchs | Mold and Device for Marking Work Pieces |
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US20220097324A1 (en) | 2022-03-31 |
US11691362B2 (en) | 2023-07-04 |
EP3974145B1 (en) | 2023-10-25 |
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